Optical reflector

ABSTRACT

An optical reflector is formed by an array of reflecting surfaces arranged one behind another in spaced, generally parallel, relation along a main axis of the array. The reflector has entry and exit faces (11, 12) disposed on opposite sides of, and extending along, the array main axis. The spaces between the reflecting surfaces is preferably occupied by a refractive material. In this case, light entering through the entry face (11) is first refracted and then reflected before being refracted again on leaving through the exit face (12). The main extent of the reflector is unlike a conventional mirror, normal to the plane of reflection. The reflector is thus well suited for use as a vehicle external rearview mirror as it has minimal lateral protection. A reflector array may be produced from a stack of elongate elements having optically worked faces.

BACKGROUND OF THE INVENTION

The present invention relates to an optical reflector suitable for awide range of use including, for example, use as an external vehiclerear view mirror.

A conventional reflector, or plane mirror, such as used, for example, asan external rear view mirror of a vehicle, can present problems due toits substantial lateral extent, that is, its extent in the plane of thereflector. Such problems include aerodynamic drag exerted by laterallyprojecting exterior mirrors. At medium and high speeds, the aerodynamicdrag factor may account for up to 80% of the total mechanical energyloss resulting in both increased fuel consumption and noise.Furthermore, although exterior rear-view mirrors are designed to yieldunder impact, they remain a traffic hazard. Mirror yield is of mostbenefit in very low speed impacts. In higher speed impacts, whetheragainst another mirror or a pedestrian, mirror inertia plays animportant role and considerable damage and/or injury can occur.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide an opticalreflector. The optical reflector of the present invention is suitablefor use as a motor vehicle rear-view mirror, but this example is givenwithout prejudice to the generality of the invention which can also beapplied to a wide range of other uses.

According to one aspect of the present invention, there is provided anoptical reflector having a plurality of elongate elemental reflectors inan array spaced from one another in a direction generally parallel tothe optical axis of each individual elemental reflector whereby toprovide a composite image of an object viewed from at least a limitedrange of angles to one side of the array, in which each elementalreflector is formed as a transparent face or facet of a transparent bodyhaving two opposed surfaces, such that light entering the reflectorthrough one said surface and approaching the face or facet through thebody at a certain angle or range of angles thereto is reflected by totalinternal reflection and exits the reflector through the other of thesaid surfaces, and such that light approaching the face or facet throughthe body at angles other than the said certain angle or range of anglesis transmitted therethrough.

The elemental reflectors preferably all lie generally parallel to oneanother, with the optical axis of the reflector as a whole parallel tothe optical axis of the individual elemental reflectors.

With such an arrangement, the main extent of the optical reflector isgenerally parallel to the optical axis of the reflector array (thisbeing normal to the plane of reflection of the elemental reflectorswhich facilitates the use of the reflector in applications such as for avehicle rear view mirror.

The transparent body consists of refractive material chosen such that amedium of lower refractive index, typically defining the interface atthe said transparent face or facet, allows total internal reflection totake place.

Embodiments of the reflector may be formed in which, at least one of theentry and exit faces is provided with slots in the refractive-materialbody, these slots extending towards the opposite face and being soarranged that one surface of each slot constitutes a respective one ofthe said surfaces.

The size and/or inclination of the elemental reflecting surfaces mayvary progressively along the array of reflecting surfaces. Furthermore,the axis of the array may be curved to enhance the viewing of closeobjects.

Preferably, the entry and/or exit faces on the refractive-material bodyhas a respective elemental refractor facet associated with each saidreflecting surface, each such facet being angled to the main axis of thearray such as to modify the optical characteristics of the reflector.The physical parameters of the elemental refractor facet may be suchthat they vary progressively along the array.

The optical reflector can be combined with one or more refractingdevices positioned across the entry and/or exit faces of the reflectorto provide an optical reflector assembly having particularcharacteristics. Preferably, one surface of the refracting device isprovided with multiple refracting faces. Where the optical reflector isformed by a refractive-material body provided with slots along one face,then the said one surface of the refracting device may be disposedadjacent to, and facing towards, the face of the reflector provided withthe slots. As a result of this arrangement, the elemental reflecting andrefracting surfaces of the overall assembly are internal of theassembly.

Light absorbing surfaces may provide for absorbtion of light which isnot subject to the intended reflection and, where applicable,refraction.

The optical reflector can, with advantage, be used as a vehicle externalrear-view mirror and to this end, the reflector can be provided withappropriate means for attaching it to a vehicle. Alternatively, it maybe formed as part of a vehicle. Where the reflector is used as anexternal rear-view mirror on a vehicle, the array of reflecting surfaceswill extend generally along the vehicle. Preferably, the end of thearray nearer the front of the vehicle lies further from the longitudinalcentre line of the vehicle than the end of the array near the vehiclerear. As a result, light at a narrow angle to the vehicle longitudinalaxis can reach the forward end of the mirror which is the mirror partthat processes this light; light from a wider angle is processed by theportion of the mirror lying nearer the rear of the vehicle. In order toreduce further the external extent of the mirror, the rear part of themirror can, advantageously, be arranged to lie inside the naturalenvelope of the vehicle.

Various forms of optical reflector embodying the present invention willnow be particularly described, by way of non-limiting example, withreference to the accompanying diagrammatic drawings, in which;

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the optical behaviour of light incident upon anoptical reflector which does not constitute an embodiment of the presentinvention, comprising an array of elemental reflectors separated by air;

FIG. 2 illustrates the optical behaviour of light incident on an opticalreflector embodying the present invention, in which an array of spacedelemental reflectors are defined by a body of refractive material;

FIG. 3 illustrates the optical behaviour of light incident on a opticalreflector embodying the present invention in which a body of refractivematerial is slotted to provide an array of spaced elemental reflectorfacets surfaces at which reflection occurs by total internal reflection;

FIG. 4 is a diagram similar to FIG. 3 but showing another form ofoptical reflector;

FIG. 5 is a diagram similar to FIG. 3 but showing a further form ofoptical reflector;

FIG. 6, is a diagram similar to FIG. 3 but showing a variation in theform of an optical reflector;

FIG. 7 is a beam field diagram for optical reflectors embodying theinvention in the case of monocular vision;

FIG. 8 is a beam field diagram for optical reflectors embodying theinvention in the case of binocular vision;

FIG. 9 is a beam field diagram showing a preferred mounting alignment ofthe optical reflector when used as a vehicle rear-view mirror;

FIG. 10 is a diagram similar to that of FIG. 9 but showing how thevehicle window contour can be adapted to reduce the projection of theoptical reflector beyond the natural envelope of the vehicle;

FIG. 11 is a diagram similar to that of FIG. 9 but with an additionalrefractor interposed in the beam path;

FIG. 12 is a diagram of a first optical assembly in which animplementation of the third form of optical reflector is combined with arefractor;

FIG. 13 is a diagram of a second optical assembly in which anotherimplementation of the third form of reflector is combined with anotherrefractor;

FIG. 14 is a diagram of a third optical assembly in which a furtherimplementation of the third form of reflector is combined with a furtherrefractor; and

FIG. 15 is a schematic view of a further embodiment of the inventionsuitable for use as a motor vehicle rear-view mirror.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The general stacked array optical reflector, shown in FIG. 1 forms partof the state of the art useful for explaining the invention. Itcomprises an array of elemental reflectors 10, constituted, for example,by silvered mirrors. These elemental reflectors are arranged one behindanother in spaced, generally parallel relationship along a main axis ofthe array. It will be understood that, in FIG. 1, the middle one of thethree entry rays shown in fact represents two rays, one of which isreflected at the central elemental reflector 10 and the other, anadjacent ray which continues on to the next reflector face.

One side of the array of reflectors constitutes an optical entry face 11for the reflector whilst the opposite side of the array constitutes anoptical exit face. Taking the optical reflector in isolation, the roleof the entry and exit faces is interchangeable. As can be seen, asubstantial portion of the light entering the reflector through theentry face, undergoes a single reflection before exiting the reflectorthrough the exit face 12.

For distant objects, the image formed by the elemental reflectors of theFIG. 1 reflector are compounded by the eye to form a composite imageindistinguishable from that produced by a conventional mirror.

It should be noted that the physical size of the elemental reflectors 10is not critical but a small size, typically less than one millimeter,can in some circumstances produce a subjectively better quality imagethan a larger size of typically more than five millimeters. Thisphenomenon is associated with the relative sizes of the elementalreflectors and the diameter of the pupil of the eye.

When the FIG. 1 reflector is viewed at angles other than the optimum ordesign angle, a proportion of the light from the object viewed is lostto the eye and, more significantly, a proportion of the light thatenters the eye does not emanate from the object. In the case of thereflector illustrated in FIG. 1, this proportion of spurious light isabout 5% for every degree of view angle away from optimum.

FIG. 2 shows an optical reflector embodying the present invention. TheFIG. 2 reflector is similar to that of FIG. 1 but now the spaces betweenthe reflectors 10 have been filled by a refractive material in the formof blocks 14 of an acrylic medium. The increased lateral extent of thereflectors 10 in FIG. 2 is solely a result of the refraction that occursas light crosses the air/block interfaces. The phenomenon of refractionis also responsible for an advantageous reduction in the spurious lighteffect for non-optimum viewing angles to about 2% per degree.

Another consequence of refraction at the entry and exit faces 11, 12 isthat, for all practical viewing angles, the angle of incidence of thelight at the reflectors 10 is greater than the critical angle for theacrylic medium. This means that the silvered reflectors 10 can dispensedwith because each acrylic block is backed by air since reflection willtake place by total internal reflection (TIR). It has been found that asatisfactory optical reflector can be made from a stacked array ofoptically transparent rods or strips, such as glass or an acrylicmaterial, having generally flat parallel faces. The interfaces betweentwo adjacent strips or rods in practice traps a small amount of air,which results in the total internal reflection of light incident on theface from within the body of the rod or strip; this occurs even if thecontacting faces are optically flat since a very small quantity of airis nevertheless trapped between the two faces. Various otherimplementations of optical reflector relying on TIR are described belowwith reference to FIGS. 3 to 6.

In the optical reflector shown in FIG. 3, a single block of refractivematerial 15 (for example, an acrylic material) has two opposed faces 16,17 that constitute optical entry and exit faces for the reflector. Theentry face 16 is formed with a plurality of wedged-shaped slots 18 thatextend from the face 16 part of the way through the block 15 towards theface 17. One surface 19 of each slot 18 forms an elemental reflectorfacet at which light approaching through the block 15 suffers a totalinternal reflection. The elemental reflector facets 19 are arranged onebehind another in a spaced, generally parallel, relationship to form anarray having a main A axis that extends along, and intermediate, theentry and exit faces 16,17 of the block 15.

As in the FIG. 2 reflector, a substantial portion of the light incidenton the FIG. 3 reflector first undergoes refraction at the entry face 16before being reflected at the elemental reflector facets 19 andundergoing further refraction at the exit face 17.

As can be seen from FIG. 3, it is not necessary for the elementalreflector facets 19 to extend the full width of the block 15 nor for therefracting interfaces to be up against the end of the reflector facets19 (see the exit face 17 in FIG. 3). It should be noted that the raysshown in FIG. 3 and subsequent Figures are typical rays rather thanlimit rays, this being done in order to facilitate an understanding ofthe invention.

The optical reflector shown in FIG. 4 is similar to that of FIG. 3 butin this case the wedge-shaped slots 18 are formed in the exit face 17 ofthe block 15. In addition, the exit face 17 has been configured suchthat the elemental refractive facet 20 associated with each respectiveelemental reflector facets 19 lies at an angle to the general directionof extent of the exit face 17. The angling chosen for each refractivefacet 20 is such as to impart desired optical characteristics to theoptical reflector, such as modifying image size.

The optical reflector shown in FIG. 5 is similar to that of FIG. 4.However, in this case, not only has the exit face of the block beenconfigured to provide angled refracting facets 20, but the entry face 16has been similarly configured to provide refracting facets 21.

The required profiles of the optical reflectors of FIGS. 3,4 and 5 can,in principle, be produced by a number of different processes including,for example, where thermoplastic materials are involved, by injectionand by compression moulding. Furthermore, as the profiles of the block15 will generally be linear normal to the plane of the Figures, thedesired profiles can be formed by rolling or turning processes.

The attractions of such rotary processes include relatively low cost oftooling and economic manufacture by a continuous flow type of productionline.

Although forming the reflector block 15 in one piece from sheet materialis generally to be preferred, other ways of constructing the reflectorsare possible. Thus, for example, reflectors of the general form shown inFIGS. 3,4 and 5 could be formed from discrete components as isillustrated in FIG. 6. More particularly, the FIG. 6 reflector comprisesa plurality of refractive-material elemental blocks 22 fastened together(for example, at their ends) into the illustrated configuration with onesurface of each block 22 providing an elemental reflecting surface 23.As with the reflector of FIG. 5, the FIG. 6 reflector has angledrefractive facets 24 and 25 on both the entry and exit sides 26, 27 ofthe reflector.

The optical properties of the reflectors described above will now bediscussed with reference to FIGS. 7 and 8. The principal difference inoperation between the described optical reflectors and that of aconventional mirror is the behaviour of the object beam; the object beamis the ray pattern obtained on the object side of the reflector bytracing rays backwards from the eye(s) to the object. FIG. 7 illustratesthe behaviour of the object beam for monocular vision while FIG. 8demonstrates the same behaviour for binocular vision; in both cases theoptical reflector of the invention is reference 30.

For distant objects, all the ray angles are the same as for aconventional mirror and viewing takes place normally. For nearerobjects, however, some eye accommodation is required. This accommodationis in two forms, namely eye focus for each eye individually, and eyealignment for one eye related to the other.

Focusing requirements become significantly different from those of aconventional mirror only for very close objects, when the ray pathlength is considerably less than one meter, and so may be neglected formost applications including vehicle rear vision systems.

Alignment of the eyes, which is favourably parallel for distant objects,needs to be made to diverge for binocular vision of close objects, andthis is not a natural action of human eyes. However, the amount ofdivergence required for objects more than five meters distance is verysmall, and this is easily accommodated by normal eyes. If binocularvision is required for objects closer than this, then a very smallamount of curvature (that is convex towards the observer) may be appliedto the optical reflector 30, typically a radius of curvature of a fewtens of meters; this will obviate the need for the eyes to diverge atall.

Stronger curvature, of the order of one meter radius, may be used inconjunction with progressively changing values of one or more physicalparameters of the elemental reflecting surfaces and/or elementalrefractor facets in order to achieve specific optical or physical designcharacteristics. The physical parameters subject to such alteration may,for example, include the surface/facet dimensions and their inclination.Of course, progressive variation of the physical parameters can beeffected independently of any curvature applied to the optical reflectoras a whole.

The described optical reflector can be advantageously used in a varietyof applications where significant lateral extent of the reflector in theplane of the reflection is undesirable. One such application is the useof the reflector as an external rear-view mirror for a vehicle. FIGS. 9and 10 illustrate use of the optical reflector 30 in such anapplication. From the earlier Figures it will be noted that narrow angleobject rays are processed by the more distant end of the reflector andwide angle ones by the rear end. This characteristic of the reflectorhas important implications particularly when the reflector is used as avehicle exterior rear-view mirror. More particularly, as can be seen inFIG. 9, the reflector 30 is best disposed at an angle to thelongitudinal axis B of the vehicle with its front end 31 further fromthis axis than its rear end 32 (in FIG. 9, the exterior of the vehicleis to the right of the vehicle front side window glass 33, the vehicleillustrated being a right-hand drive vehicle). It will be noted that nopart of the reflector 30 protrudes beyond that part of the reflectorwhich reflects the narrowest angle ray; this, of course, is in contrastto a conventional mirror where the majority of the mirror protrudesbeyond the part which reflects the narrowest angle ray.

This property of the reflector 30 may be used to obtain an improved viewbehind the vehicle or it may be used to reduce even further the exteriorprotrusion of the reflector. This latter possibility is illustrated inFIG. 10 where the side window glass 33 is illustrated as having beengiven a particular inwardly angled form enabling protrusion of thereflector 31 to be minimised while still permitting a view down the sideof the vehicle.

With the described reflector, except in the case of symmetry of bothphysical geometry of the reflector and the entry and exit light beams,optical aberrations are present in the image beam. However, by carefuldesign using design criteria known to persons skilled in the art, theseoptical aberrations may generally be kept within the bounds ofsubjective acceptability.

If required, additional refractors may be interposed in either or bothof the entry and exit beams to condition further the optics and theserefractors may either be of the solid or Fresnel prism type. Thus, forexample, FIG. 11 illustrates the use a Fresnel prism type refractor 40interposed in the entry beam for the optical reflector of FIG. 10. Itwill be appreciated that one or more refractors may also be positionedbetween the reflector 30 and the observer instead of or as well as therefractor shown in FIG. 11. Moreover, conventional prism refractors maybe employed rather than Fresnel prisms. Although such prisms are shownin close proximity to the reflector they could be located spacedtherefrom, especially if this facilitates the passage between them of anopening side window.

Design flexibility of the assembly of the optical reflector and one ormore additional refractors is enhanced not only by the choice ofgeometry for each additional refractor but also by the material used forthe refractor; advantageously, this material may possess a differentrefractive index and dispersive power from that used for the opticalreflector of FIG. 2 onwards. FIG. 12 illustrates a preferred assembly ofoptical reflector 41 and an additional refractor 42, the reflector 41being of the general form illustrated in FIGS. 3 to 6 in the FIG. 12example, the additional refractor 42 being an object beam refractor and,as can be seen, the refractor being formed with precision refractingfacets 43 along one face 44. This face 44 is turned towards the slottedentry face 45 which is also formed with precision, angle refractingfacets 46. Although in FIG. 12 the reflector 41 and the refractor 42 areshown spaced part, in the final assembly these elements are preferablyin contact with each other to form a robust body in which the precisionrefracting and reflecting elemental facets of the assembly lieinternally and are protected from abrasion, dust and other potentialenvironmental damage.

FIG. 13 shows another assembly of an optical reflector 51 of the generalform shown in FIGS. 3 to 6, together with an additional image beamrefractor 52, the two components being shown in their assembledposition. As with the FIG. 12 assembly, the arrangement of FIG. 13provides protection for the precision elemental reflecting andrefracting elemental facets of the assembly.

FIG. 14 illustrates an assembly similar to that of FIG. 13 but forsimplified configurations of optical reflector 51 and image-beamrefractor 52.

FIG. 15 shows in schematic form a mirror 60 suitable for any applicationwhere the field of view is wide, for example, for use in a motor vehiclerear-view mirror. In such an application, because the reflected imagemay be viewed over a relatively wide angle, typically between 30° and45°, the angle subtended at the eye by the two opposite edges of areflector in the forward part of the reflector assembly, which isfurther from the eye, is rather greater than the angle subtended at theeye by the rearwardly located reflectors. This could result in a brokenimage if an embodiment such as that shown in FIGS. 1 and 2 is used forthis purpose since constant spacing between reflectors and constantreflector width would allow light to reach the observer from a pointforward of the observer by transmission through the assembly betweenadjacent reflectors as shown by way of example by the arrow X in FIG. 1.It will be appreciated here that in the description of the embodiment ofFIG. 1 the position of the observer was assumed to be somewhat furtherto the rear so that in practice light arriving along the path of thearrow A would not reach the observer's eyes; however, if the observer'sposition was different and had to be, for example, closer to the opticalreflector or more forwardly located than previously assumed, then lightfrom the position of arrow A could arrive at the observer's eye andresult in a broken image. In order to overcome this potential problemone of two alternative modifications to the reflector arrays of thepreceding Figures may be employed, namely the spacing between reflectorsmay be varied along the length of the array or the width of thereflectors may be different along the length of the array. One exampleof this latter arrangement is illustrated in FIG. 15, where it will beseen that the width of the reflectors 61 increases towards the rear ofthe array such that no light can reach the observer by directtransmission through the array. Ideally, in the viewing position shown,and considering just two of the reflectors, 61a, 61b of the array, theright hand edge of the reflector 61a furthest from the observer shouldbe in alignment with the left hand edge of the nearer reflector 61b atthe observer's eye. Obviously this is an idealised situation since itdoes not take into account binocular vision or the fact that theobserver's head, and therefore his eyes, do not occupy a fixed locationin space but may move around within a limited volume. In fact toaccommodate both of these factors a small degree of overlap rather thanexact alignment may be tolerable. It will be appreciated, however, thatany overlap will result in a certain loss of light through thereflector. In most illumination conditions this is tolerable, andappropriately handled, e.g. by using black surfaces for anynon-transmissive or non-reflective faces of the device, will not resultin any appreciable problems.

The embodiment of FIG. 15 is made from a stacked array of strip-likeelements 62 each having two opposite substantially parallel faces 62a,62b (see inset to FIG. 15, which illustrates just one such element) theinterface between each of which and the contacting opposite face of thenext adjacent element defines the reflector 61 by total internalreflection. The other opposite faces 62c, 62d of the element 62 are notparallel to one another in this embodiment, but rather define atrapezoidal section. Of course, in other embodiments these faces mayindeed be parallel.

For any design using discrete elemental with at least two opposite facesparallel, the use of ordinary float glass offers potential savings inmanufacturing complexity. For example, if the float faces are therefractor faces, then only one further face, namely the reflector, needsto be optically worked. Furthermore, designs based on discrete elementshaving at least one pair of opposing faces parallel are particularlyeasy to assemble with the necessary accuracy. This may be done, forexample, by simply sandwiching the elements between additional sheets offloat glass.

It has been found that in practice the aspect ratio, that is the ratiobetween the optical width of the reflectors and the spacing betweenreflectors is preferably of the order of 3:2. A practical embodimentemploys a stacked array of elements 3 mm wide and 2 mm thick.

It will be appreciated that the various modifications and additions arepossible to the described optical reflectors. Thus, for example, varioussurfaces of the reflector (and, where provided, any additionalrefractors) can be blackened--that is, provided with light absorbingcoating--in order to reduce the intensity of light rays not passingthrough the reflector along the desired optical path.

Although the currently intended primary use of the invention relates toreflection of visible light, the term `optical` is to be understood in abroader sense, including, for example, infra-red radiation.

In the embodiment of FIG. 11, it will be appreciated that the incidentlight rays arriving from an object to the rear of the vehicle have beenillustrated at a much shallower angle to the longitudinal centreline ofthe vehicle than the reflected rays which are directed from thereflector 30 towards the observer's eyes. This asymmetry can be achievednot only by positioning the array of reflectors as a whole, as is shownin FIG. 11 but also by appropriate orientation of the individualelemental reflectors within the array. Thus, for example, by appropriateorientation of the elemental reflectors, the light paths of theembodiments of FIGS. 1 to 8, all of which have been shown symmetrical,could be made asymmetrical to take account of particular conditions, notonly for use as a vehicle rear view mirror but for any of the other widerange of uses to which the optical reflector of the present inventionmay be applied. This asymmetry or "handing" of the entry and exit beamsmay also be facilitated by the use of refractors on the entry and exitsides of the reflector.

Furthermore, curvature of the reflector array either in a convex orconcave sense (towards the observer) may be achieved by appropriateorientation of the element reflectors as well as curvature of the arrayitself by locating the reflectors in a non-rectilinear line. In thisway, it may be arranged that the focal position is not necessarilysymmetrical, nor necessarily the same in two planes orthogonal to oneanother. In other words, it is envisaged that the elemental reflectorsmay, themselves, be composed of sub-elements each of which may beinclined differently from its neighhour to a given flat plane.

What is claimed is:
 1. An optical reflector comprising a plurality ofelongate elemental reflectors in a longitudinally directed array of suchand spaced from one another in a direction generally parallel to areflector optical axis whereby to provide a composite image of an objectviewed from at least a limited range of angles to one side of the array,wherein each of said elemental reflectors is formed as a transparentfacet of a transparent body having two opposed surfaces, whereby lightentering said reflector through one of said surfaces and approachingsaid transparent elemental reflector facet through said body at an anglewithin a predetermined range of angles thereto is reflected by totalinternal reflection at said transparent elemental reflector facet andexits said reflector through the other of said surfaces, and wherebylight approaching said transparent elemental reflector facet throughsaid body at angles outside said range of angles is transmittedtherethrough.
 2. The optical reflector of claim 1, wherein saidelemental reflectors are defined at the interfaces between a stackedarray of elongate elements.
 3. The optical reflector of claim 1 whereineach said transparent elemental reflector facet is formed as a surfaceof a body of refractive material having sides that constitute said twoopposed surfaces.
 4. The optical reflector of claim 3 further includingat least one refractor positioned in a light path from an object to anobserver via said at least one refractor and wherein one surface of saidat least one refractor is provided with multiple refracting facets, saidat least one refractor being assembled with said reflector such thatsaid one surface of said reflector faces towards a face of saidreflector which is provided with slots.
 5. The optical reflector, ofclaim 4 wherein all refracting faces of said refractor and all thereflecting surfaces of said reflector are internal of the assembledreflector/refractor structure.
 6. The optical reflector of claim 3,wherein said body of refractive material comprises a plurality ofelements joined together, each element having a surface which provides arespective one of said facets.
 7. The optical reflector of claim 1,wherein a physical parameter comprising one of a dimension, and aninclination relative to an exit associated surface of said elementalreflecting facets changes progressively along said array.
 8. The opticalreflector of claim 1, wherein said array is curved along an array mainaxis.
 9. The optical reflector of claim 1, wherein said array is taperedalong an array main axis.
 10. The optical reflector of claim 1, whereinone of said opposed surfaces has, for each said transparent elementalreflector facet, a respective elemental refractor, said elementalrefractor being angled such as to modify the optical characteristics ofsaid transparent elemental reflector facet.
 11. The optical reflector ofclaim 10, wherein a physical parameter comprising one of a dimension,and an inclination relative to an associated reflecting facet of eachsaid elemental refractor changes progressively along said array.
 12. Theoptical reflector of claim 1, further including at least one refractorpositioned in a light path from an object to an observer via saidreflector.
 13. The optical reflector of claim 12, wherein said twoopposed surfaces are oriented such that light entering said transparentbody through a said surface is refracted towards a reflector facet andlight exiting said transparent body through a said surface afterreflection at a said facet is subject to refraction.
 14. The opticalreflector of claim 12 adapted as a rear view mirror for a vehiclewherein a forward end of said refractor lies further from a longitudinalcenter line of said vehicle than a rearward end thereof, and a forwardend of said reflector array lies nearer the longitudinal centerline ofsaid vehicle than a rearward end thereof.
 15. The optical reflector ofclaim 14, wherein a rear part of said mirror lies inside an envelope ofsaid vehicle whereby to minimize a lateral projection of said mirrorbeyond said envelope.
 16. The optical reflector of claim 1, wherein thespacing between adjacent elemental reflectors varies along the arraythereof.
 17. The optical reflector of claim 1 adapted as a rear-viewmirror for a vehicle wherein said array nearer a forward end of thereflector lies further from a longitudinal centerline of said vehiclethan an end of the array nearer a vehicle rear.
 18. The opticalreflector of claim 1, wherein the dimensions of each said transparentelemental reflector facet in a direction transverse said array thereofbetween said two opposed surfaces is less than 1 mm.
 19. An opticalreflector comprising a plurality of elongate elemental reflectors in alongitudinally directed array of such and spaced from one another in adirection generally parallel to a reflector optical axis whereby toprovide a composite image of an object viewed from at least a limitedrange of angles to one side of the array, wherein each of said elementalreflectors is formed as a transparent facet of a transparent body havingtwo opposed surfaces, whereby light entering said optical reflectorthrough one said surfaces and approaching a said transparent elementalreflector facet through said body at an angle within a predeterminedrange of angles thereto is reflected by total internal reflection atsaid transparent elemental reflector facet and exits said reflectorthrough the other of said surfaces, and whereby light approaching saidtransparent elemental reflector facet through said body at anglesoutside said range of angles is transmitted therethrough, each saidtransparent elemental reflector facet being formed as a surface of abody of refractive material having sides that constitute said twoopposed surfaces, and at least one of said two surfaces having slotsextending towards the other said surface, one face of each said slotconstituting a respective one of said transparent elemental reflectorfacets.
 20. The optical reflector of claim 19, wherein said body ofrefractive material is formed in one piece.